TABLE 4.

Effect of Ca ions on the amplification capacities of nine thermostable DNA polymerases

DNA polymerase	PCR resultsa with CaCl2 concn (mM)b of:
	0.2	1.0	2.0	4.0	6.0	8.0	10.0
AmpliTaq Gold	++	−−	−−	−−	−−	−−	−−
Expand High Fidelity	++	++	++	−−	−−	−−	−−
HotTub	++	++	++	++	−−	−−	−−
Pwo	++	+−	−−	−−	−−	−−	−−
rTth	++	++	−−	−−	−−	−−	−−
Taq	++	−−	−−	−−	−−	−−	−−
Tfl	++	++	+−	−−	−−	−−	−−
Tli	++	++	−−	−−	−−	−−	−−
Ultma	++	++	−−	−−	−−	−−	−−

^aTwo independent PCR results. Symbols: +, band of good intensity; ±, band of low intensity; −, no band. 

^bConcentrations of CaCl₂ in the PCR mixtures containing 1 ng of L. monocytogenes DNA.